The invention concerns a procedure for packaging food under protective gas in synthetic material containers with flexible covers.
Such procedures are performed step by step and include as the packaging steps, the steps of filling the product into the containers, flushing with a protective gas, applying the covers, and welding the covers closed. The flushing with the protective gas takes place by blowing the protective gas, e.g. nitrogen, carbon dioxide, or argon, into the container filled with the product, from above via one or several gas nozzles. It is obvious that in such a procedure, great specific quantities of the protective gas will be required in order to fill the headroom in the container with protective gas. The container, filled with the product, usually has a headroom of from 50 to 100 ml, shaped as a flat plate of max. 10 mm thickness. A sufficient gas exchange in this open headroom is possible only if the flushing is performed with quantities of protective gas amounting to several times the volume of the headroom. This procedure is thus unsatisfactory, already from the point of view of requirements for protective gas. An additional disadvantage of this process is that it is impossible to avoid infiltration of oxygen from the air in the headroom filled with the protective gas. After the flushing with the protective gas, it takes an additional time of approx. 2 seconds until the container is provided with a cover. This idle time causes renewal of the gas exchange, the oxygen content increases again. Furthermore, when the cover is applied, even more air is forced into the headroom of the container and enclosed there.